1. Field of the Invention
The present invention relates to a golf club head that is helpful for increasing a region of a high coefficient of restitution so as to increase carry for a golfer of average skill.
2. Description of the Background Art
Importance is placed on the function of increasing the carry of a hit ball of a golf club head, in particular, a wood type golf club head. Therefore, a variety of methods for increasing the coefficient of restitution of the head has been proposed by respective golf club manufacturers. According to one of such methods for increasing the coefficient of restitution of the head, a structure is known where a thin portion in annular form is provided on the back side of the face portion so that the face bends sufficiently at the time when a ball is hit as described in the Published patent application No. H09-192273, or No. H09-299519. In addition, it is known that a thin portion where the thickness has been reduced is provided in an arbitrary region of the face portion, as described in the Japanese Translation of PCT International Patent Publication No. WO99/36132, or Published patent application No. 2001-29523.
According to conventional methods, although attention is paid to increasing the value of the coefficient of restitution, an idea to extend the “region” with a high coefficient of restitution is not provided. On the other hand, it is unreasonable to expect a golfer of average skill to always hit a ball at the same point on the face surface. Accordingly, in order to effectively increase carry for a golfer of average skill, it becomes important to form a region of a high coefficient of restitution in a wider range of the face portion, in addition to increase in the numeral value of the coefficient of restitution. However, this hasn't been sufficiently attempted yet in conventional heads.